What Is Respiration In Biology?

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Respiration refers to a metabolic process, which occurs in all organisms. Respiration is a biochemical process that occurs within an organism's cells.

In the respiration process, the energy in the form of ATP, i.e., Adenosine triphosphate, is produced by glucose breakdown, which is then used by cells for performing several functions. Two different types of respiration take place in organisms. Let us have a detailed look at it:

Respiration Types!  
       
Aerobic Respiration

Aerobic respiration is a cellular respiration type that occurs in oxygen's presence to produce energy. The process is a continuous one that takes place within plants and animal's cells. The whole process can be easily explained with a chemical equation:

Glucose (C6H12O6) + Oxygen (6O2) --------> Carbon Dioxide (6CO2) + Water (6H2O) + Energy (ATP)

Anaerobic Respiration

Anaerobic respiration is a cellular respiration type that takes place in oxygen's absence to produce energy. The chemical equation that can explain anaerobic respiration is:

Glucose (C6H12O6) -------------> ...
... Alcohol 2(C2H5OH) + Carbon Dioxide 2(CO2) + Energy (ATP)

Respiration Phases in Organisms!

In prokaryotic cells, the Respiration process takes place in the cytosol and around the plasma membrane, whereas, in eukaryotic cells, respiration occurs in mitochondria. Mitochondria are also considered as the cell's powerhouse.

However, this process is somewhat similar to a car engine's internal combustion, wherein the oxygen and organic compounds go in while the carbon dioxide and water come out.

The three phases of respiration include:

Phase 1
Glycolysis

The glucose molecules get transformed into pyruvic acid that is further oxidized to carbon dioxide and water, leaving two carbon molecules, namely, acetyl-CoA. During the glycolysis process, the two molecules of NADH and ATP are produced. Pyruvate enters mitochondria's inner matrix and undergoes oxidation in Kreb's cycle.

Phase 2

Oxidative Phosphorylation

Oxidative phosphorylation is a process where the ATP molecules are produced as an outcome of electron transfer from FADH2 or NADH to O2 by an electron carrier's series. This whole process takes place within a cell's mitochondria.

Phase 3

Citric Acid Cycle

The citric acid cycle is also known as Kreb's cycle or tricarboxylic acid cycle. Two ATP molecules are formed in each phase of Kreb's cycle and occur within a cell's mitochondrial matrix. However, the electron produced in Kreb's cycle moves across the mitochondrial matrix.
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